How to move a reply to a new topic?

Someone starts a topic on my forum. As there are more replies, eventually the conversation shifts away from the original topic.

When someone posts a reply to a thread, which should really be it’s own new topic and reside in a different forum, as the administrator, I’d like to move that person’s reply out of the thread they posted in, and into their own new thread, usually in another forum.

I know you can MOVE topics from one forum to another, but that moves ALL replies in that thread. I’m trying to break out one reply from a thread and move it to it’s own new thread.